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Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Materialteknik) > Björkman Bo

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1.
  • Brämming, Mats, et al. (författare)
  • BOS vessel vibration measurement for foam level detection
  • 2011
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 51:1, s. 71-79
  • Tidskriftsartikel (refereegranskat)abstract
    • In the BOS process liquid slag together with dispersed metal droplets, solid particles and process gases form an expanding foam. Certain process conditions may lead to excessive foam growth, forcing foam out through the vessel mouth, an event commonly known as 'slopping'. Slopping results in loss of valuable metal, equipment damage and lost production time. In the early 1980s a system for foam level and slopping control was installed at SSAB's steel plant in Luleå, a system based on the correlation between BOS vessel vibration in a narrow low frequency band and foam development. The technique, in this case with an accelerometer mounted on the trunnion bearing housing, soon showed its usefulness, for example when adapting existing lance patterns to a change in oxygen lance design from a 3-hole to a 4-hole nozzle. Estimating the actual foam height in the BOS vessel was of great importance in the recently completed RFCS funded research project "IMPHOS" (Improving Phosphorus Refining). Based on the earlier positive experiences, it was decided to further develop the vessel vibration measurement technique. Trials on an industrial size BOS vessel type LD/LBE have been carried out, this time with a tri-axial accelerometer mounted on the vessel trunnion. FFT spectrum analysis has been used in order to find the frequency band with best correlation to the foam level development. The results show that there is a correlation between vessel vibration and foam height that can be used for dynamic foam level and slopping control. © 2011 ISIJ.
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2.
  • Brämming, Mats, et al. (författare)
  • Comparison between vessel vibration and audiometry for slopping control in the top-blown BOS process
  • 2011
  • Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:6, s. 683-692
  • Tidskriftsartikel (refereegranskat)abstract
    • Excess slag foam growth is a frequent problem in the BOS process. In the worst case, foam is forced out of the vessel and this phenomenon, commonly called slopping, not only results in loss of valuable metal yield but also in equipment damage and lost production time. In order to minimize slopping, accurate estimation of the foam level inside the vessel is an important part of BOS process control. In the top blown BOS vessel, slopping control is achieved using both static and dynamic measures. The most common implemented technique for dynamic foam height estimation and slopping control is the audiometer system. An alternative method, vessel vibration monitoring, has been investigated as part of the work in a RFCS funded research project called IMPHOS. In order to judge the usefulness of this method, parallel vibration and audio measurements have been carried out on 130 tonne as well as on 300 tonne BOS vessels. The results show that during stable process conditions there is good agreement between the two methods with regard to foam height estimation and, as vessel vibration and audiometry are largely independent of each other, a combination of the two is likely to increase significantly the accuracy of slopping prediction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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3.
  • Eklund, Nicklas, et al. (författare)
  • Operation at High Pellet Ratio and Without External Slag Formers – Trials in an Experimental Blast Furnace
  • 2009
  • Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 80:6, s. 379-389, s. 379-384
  • Tidskriftsartikel (refereegranskat)abstract
    • Blast furnaces that operate with pellets and sinter normally use high basicity sinter and acid pellets to balance the slag chemistry. When external additives are used, irregular slag formation occurs due to their uneven distribution in the burden. If basic sinter is used together with a large amount of acid pellets, all additives are incorporated in the iron bearing materials with an improved burden mixture as a consequence. During a campaign in the LKAB Experimental Blast Furnace, pellets and sinter were operated at an ultra low slag volume. A high amount of pellets was balanced with high basicity sinter. An improved blast furnace operation is shown when operating at ultra low slag volume and without external slag formers. During the test period, the blast furnace operation was smooth and stable, and the reductant rate was decreased.
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4.
  • Hilding, T., et al. (författare)
  • Degradation behaviour of a high CSR coke in an Experimental Blast Furnace: Effect of carbon structure and alkali reactions
  • 2005
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 45:7, s. 1041-1050
  • Tidskriftsartikel (refereegranskat)abstract
    • A high CSR coke was tested in the LKAB's Experimental Blast Furnace (EBF) at Luleå. The evolution of physical and chemical properties of the centre-line coke samples were analysed by Light Optical Microscopy (LOM), BET N2 absorption and SEM/XRF/XRD. Alkali distribution in the EBF cokes was examined by XRF/SEM and EDS. Thermo Gravimetric Analysis (TGA) was used to measure isothermal and non-isothermal CO2 reactivity of the cokes. The crystalline order of carbon and the concentration of alkalis were found to increase as the coke descended through thermal reserve zone to the cohesive zone of the EBF. The crystallite height (Lc) of EBF coke carbon displayed a linear correlation with the measured EBF temperatures demonstrating the strong effect of temperature on carbon structure of coke in the EBF. Alkali concentration of the coke was increased as it descended into the EBF, and was uniformly distributed throughout the coke matrix. The CO2 reactivity of lower zone cokes was found to increase when compared to the reactivity of the upper zones cokes, and was related to the catalytic effect of increased alkalis concentration. The deterioration of coke quality particularly coke strength and abrasion propensity were related to coke graphitisation, alkalization and reactivity, Coke graphitisation is shown to have a strong influence on the coke degradation behaviour in the EBF. © 2005 ISIJ.
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5.
  • Hilding, Tobias, et al. (författare)
  • Effect of temperature on coke properties and CO2 reactivity under laboratory conditions and in an experimental blast furnace
  • 2005
  • Ingår i: AISTech - Iron and Steel Technology Conference Proceedings. - Warrendale, Pa : Iron and Steel Society. ; , s. 497-505, s. 497-505
  • Konferensbidrag (refereegranskat)abstract
    • Physical and chemical properties of coke samples excavated from LKAB's Experimental Blast Furnace (EBF) at MEFOS in Luleå, Sweden were characterized. A thermal annealing study the raw coke used in the EBF was also conducted in a horizontal furnace in a neutral environment at a range of temperatures up to 1650°C. Carbon crystallite height of the EBF coke and of the cokes treated in the laboratory furnace were measured by XRD while mineral phases were characterized by using SEM/EDS. The CO2 reactivity of the EBF cokes was measured by thermo-gravimetric analyser (TGA). The study demonstrated the strong effect of temperature on the modification of coke properties with special focus on carbon structure both under laboratory and experimental blast furnace conditions. The coke reactivity in the EBF was accelerated due to presence of recirculating alkalis in the coke, which increased as the coke descended in the EBF. The growth of carbon crystallite height of coke in the horizontal furnace was found to be of similar order as observed in the EBF under a similar range of temperatures. Comparison of carbon structure of laboratory treated cokes and the EBF excavated cokes indicated that carbon ordering of cokes is predominantly enhanced by the temperature rather than reacting gases or recirculating alkalis. The deterioration of coke quality such as coke strength (CSR) and abrasion propensity were related to coke graphitisation, alkalization and reactivity such that coke graphitisation was shown to have a strong impact on coke degradation behaviour. The study further implied that alkalis have a potential to influence the coke reactivity without affecting their graphitisation behaviour. The study also highlights the limitations of the CSR test for assessing the coke behaviour in an operating blast furnaces as it cannot simulate impact of graphitisation of cokes which is significant only at much higher temperatures.
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6.
  • Hooey, Lawrence, et al. (författare)
  • Role of ferrous raw materials in the energy efficiency of integrated steelmaking
  • 2014
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 54:3, s. 596-604
  • Tidskriftsartikel (refereegranskat)abstract
    • The role of ferrous raw materials and iron ore agglomeration in energy consumption of integrated steelmaking has been evaluated using a system-wide model. Four steelplant cases were defined: typical European steelplant with sinterplant; Nordic steelplant with sinterplant; European steelplant with sinter:pellet ratio of 50%, and Nordic steelplant charging pellets and a small amount of briquettes. Energy consumption in the mining system were estimated from published statistics at 150 MJ/t for lump ore and sinter fines, 650 MJ/t for pellets made from magnetite and 1 050 MJ/t for pellets made from hematite. An integrated steelplant model including all major unit operations was used to calculate overall system energy consumption from iron ore mining to hot rolled coil. Adjustments were made accounting for energy benefit of ground granulated blast furnace slag in cement production, energy required for cement production required for briquetting, and excess BF and BOF gas producing electricity in a 32% efficient power plant. The system-wide net adjusted energy in the first three steeplant cases showed marginal improvement with use of high grade sinter fines and decrease of pellet/sinter ratio to 50% compared to typical European case. Nordic steelplant charging pellets and briquettes had a reduction in system-wide energy of 5% to 8% for charging pellets from hematite or magnetite respectively compared to the typical European steelplant charging sinter and pellets made from hematite ore. Replacement of sinter with pellets was mainly responsible for the improvement with smaller contributions from magnetite ore in pelletizing.
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7.
  • Hu, Xianfeng, et al. (författare)
  • Thermogravimetric study on carbothermic reduction of chromite ore under non-isothermal conditions
  • 2015
  • Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 409-416
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, the reduction of chromite ore by coke was investigated by means of thermogravimetric analysis under non-isothermal conditions (from room temperature to 1823 K). The fractional reduced samples were examined by SEM/EDS and X-ray diffraction analyses. The experimental results showed that the reduction of iron in the chromite ore started before that of chromium in the ore, and the reduction of chromium and iron in the ore overlapped to some degree. Chromium iron carbide (Cr,Fe)7C3, was found to be the intermediate phase during the reduction, and a chromium gradient was found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process was proposed: one stage involving the reduction of iron in the chromite ore and three stages involving the reduction of chromium in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore were considered. The difficulty in the reduction of the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of the component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes further reduction very difficult.
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8.
  • Leimalm, Ulrika, et al. (författare)
  • Blast furnace pellet textures during reduction and correlation to strength
  • 2010
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:10, s. 1396-1405
  • Tidskriftsartikel (refereegranskat)abstract
    • The blast furnace is the most common means of producing hot metal. As the amounts of reduction agents increases, which influence in-furnace conditions such as ascending gas properties, temperature profiles and the ore-to-coke ratio, new demands are put on the iron-bearing material in terms of both reducibility and mechanical strength. To investigate the possibilities to use the Pellet Multi Press (PMP) equipment for compression strength measurements of reduced pellets and to gain a deeper understanding of the correlation between pellet texture and strength, an initial study of pellets taken from the LKAB Experimental Blast Furnace (EBF) was conducted. Furthermore, the pellet pieces generated after compression tests were characterized using light optical microscopy. In order to correlate the texture of pellet pieces to the pellet texture prior to breakage, a characterization of the chronological pellet texture development during reduction in the EBF was performed. The original pellet texture remained in the beginning of reduction and differences receded through the EBF shaft as wustite and Femet was formed. Occurrence of Femet in the pellet texture increased the compression strength, while less reduced and less sintered textures showed the reverse effect. So far, the results from compression strength tests indicate that disintegration of pellets takes place at a reaction front, at the transition between different texture types of iron oxide or at the location of a visible surface crack. © 2010 ISIJ.
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9.
  • Leimalm, Ulrika, et al. (författare)
  • Effect of different PCI practice on the texture obtained during reduction of iron oxide pellets
  • 2008
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:12, s. 1686-1695
  • Tidskriftsartikel (refereegranskat)abstract
    • In modern blast furnace ironmaking, producers continuously strive to reduce coke consumption by replacing coke with e.g., an increased amount of injected pulverized coal. A change in pulverized coal injection rate (PCR) and injection coal type will influence the in-furnace conditions and thus the reduction of iron oxides. In the present study, the reduction behaviour of olivine pellets and textures formed were investigated in the LKAB Experimental Blast Furnace (EBF) and in laboratory scale. In the EBF, effects of injection of an low-volatile (LV) and an high-volatile (HV) coal type at different PCR while two types of oxygen supply methods were employed were investigated. The choice of injection coal type was conclusive for the Femet texture formed during reduction, extent of Femet carburization and K distribution in the pellets. The amount of volatile matters in the coal type had a greater effect on the reduction properties than the PCR and oxygen supply method. Laboratory experiments simulating PCR, based on measurements in the EBF, showed that the initial reduction conditions, in terms of temperature level and reduction gas composition, determined the pellet texture up to a reduction degree of at least 60%. The tests carried out in the EBF showed that the pellets were well suited for blast furnace reduction under all the investigated process conditions. The laboratory tests supported this conclusion. © 2008 ISIJ.
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10.
  • Leimalm, Ulrika, et al. (författare)
  • Off-gas dust in an experimental blast furnace part 1: Characterization of flue dust, sludge and shaft fines
  • 2010
  • Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:11, s. 1560-1569
  • Tidskriftsartikel (refereegranskat)abstract
    • In blast furnace (BF) ironmaking, efforts are made to decrease coke consumption, which can be done by increasing the pulverized coal injection rate (PCR). This will cause changes in ¡n-furnace reduction conditions, burden distribution, demands on raw material strength, etc. In order to maintain stable operation, but also to obtain low amounts of material losses through the off-gas, it is important to understand fines generation and behaviour in the BF Off-gas dust and shaft fines generated in the LKAB Experimental Blast Furnace (EBF) were sampled during operation with olivine pellets and mixtures of acid pellets and sinter as iron-bearing materials. Characterization using XRD, SEM and LOM was focused on fines from iron-bearing materials, coke and slag formers. The results showed that flue dust, mainly <0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions >0.075 mm and consisted mainly of coke particles from the shaft. Fe-containing particles, as Fe2O 3 from the top of the shaft, formed the major part of flue dust fractions <0.063 mm. Particles from slag formers such as quartzite and limestone were observed in flue dust when slag formers were utilized in the feed. Sludge consisted mainly of chemically formed spherical particles <1 μm precipitated from the ascending gas as the temperature decreased. © 2010 ISIJ.
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